# Does the size of a person affect caffeines effect?

**URL:** <https://boards.straightdope.com/t/does-the-size-of-a-person-affect-caffeines-effect/717623>\
**Category:** Factual Questions\
**Created:** [April 14, 2015, 5:37am UTC](https://boards.straightdope.com/t/does-the-size-of-a-person-affect-caffeines-effect/717623 "2015-04-14T05:37:52Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![pkbites](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/pkbites/32/204_2.png) [@pkbites](https://boards.straightdope.com/u/pkbites)\
**Post date:** [April 14, 2015, 5:37am UTC](https://boards.straightdope.com/t/does-the-size-of-a-person-affect-caffeines-effect/717623/1 "2015-04-14T05:37:52Z")

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A 300 pound person can drink more alcohol without become intoxicated than a 200 pound person.

Does this same equation cross over to caffeine? At 210 pounds will a can of Red Bull have less effect on me than it will on my 150lbs nephew?

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**Author:** ![Isilder](https://avatars.discourse-cdn.com/v4/letter/i/cc9497/32.png) [@Isilder](https://boards.straightdope.com/u/Isilder)\
**Post date:** [April 14, 2015, 10:14am UTC](https://boards.straightdope.com/t/does-the-size-of-a-person-affect-caffeines-effect/717623/2 "2015-04-14T10:14:09Z")

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Yes

The substance caffeine rapidly moves into the blood plasma and flesh and organs…  
A bigger person has more plasma and flesh for it to move into…  
Thus the concentration is related to the amount imbibed .

The action is related to concentration, as its a dynamic equilibrium when the caffeine competes with adenosine… that is, the overrall rate of binding is related to the probably of a receptor being hit by adenosine or caffeine… and not losing it…  
so the higher the concentration of caffeine, the greater the effect of its override of adenosine…

It also stands to reason , but not entire sure, that more caffeine intake produces more adrenaline, This may be individual, as its indirect (more of a switch than an equilibrium system )

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**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\
**Post date:** [April 14, 2015, 11:15am UTC](https://boards.straightdope.com/t/does-the-size-of-a-person-affect-caffeines-effect/717623/3 "2015-04-14T11:15:32Z")

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Isildur, do you have a quick and dirty explanation for why some drugs are dosed by body weight and most aren’t? I get asked that all the time and I don’t have a good answer.

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**Author:** ![Broomstick](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/broomstick/32/246_2.png) [@Broomstick](https://boards.straightdope.com/u/Broomstick)\
**Post date:** [April 14, 2015, 11:43am UTC](https://boards.straightdope.com/t/does-the-size-of-a-person-affect-caffeines-effect/717623/4 "2015-04-14T11:43:16Z")

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I always thought it was because for some drugs exact dosage was more important than for other drugs.

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**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\
**Post date:** [April 14, 2015, 2:12pm UTC](https://boards.straightdope.com/t/does-the-size-of-a-person-affect-caffeines-effect/717623/5 "2015-04-14T14:12:32Z")

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if you were given an amount that would saturate all pathways then a body weight dosage wouldn’t have an effect.